Die casting machine plunger tip



June 11, 1963 MORTON DIE CASTING MACHINE PLUNGER TIP Filed Aug. 25, 1959 INVENTOR. 3 GLEN R. MORTON 3,692,880 DIE CASTING MAC PLUNGER TE Glen R. Morton, 7025 Sarpy St, Omaha, Nebr. Filed Aug. 25', 1959, Ser- No. 836,004 1 (Hahn. (Cl. 22-68) This invention relates to the die casting machine plunger tips and more particularly it is an objective to provide a plunger tip which is adapted to maintain a better fit in the shot cylinder, operating at substantially no clearance as is of particular value in vacuum die casting machines but is valuable on non-vacuum machines as well.

In the prior art when a vacuum is drawn on a cavity and therefore also on a shot cylinder, the vacuum reduces the pressure in the shot cylinder suificiently that atmospheric pressure pushes the molten metal from the molten metal bath up into the shot chamber, as is desirable and as is one of many of the great advantages of the use of vacuum in die casting. However, with this advantage comes the disadvantage of air leaking past the plunger tip while it is in its retracted position before injection. This air leakage is extremely serious because the air leaks in and mixes right with the molten aluminum as the aluminum is pulled upwardly into the shot chamber.

As a result, upon injection the air is carried into the cavity with the molten aluminum whereby even though the most highly effective equipment has been used to draw the vacuum from the cavity, and even though the cavity itself is evacuated thoroughly all in an attempt to provide a dense casting without air pocketsnonetheless when the molten metal is carried up into the cavity it carries with it air that is so undesirable because it causes the casting to be so poor as to be of an unsightly blistered appearance with many large blisters and many small blisters, resulting in a most unmarketable casting.

The result of air leakage can be each summarized by saying that even though an ideal amount of vacuum has been drawn on the cavity and shot chamber, it is all for no avail because the desired result of a dense, non-porous casting without air pockets or blisters fails to be attained.

I have even found that the number of blisters and air pockets is greater when a die casting machine is run with a vacuum than when the machine is run without any vacuum at all, although one would normally assume that the reverse would be the case. This comes about because atmospheric'pressure at 14.7 pounds per square inch has been leaking rapidly into the molten aluminum ruining the molten aluminum while the shot chamber is loading with aluminum.

The amount of turbulence of air flowing into the molten aluminum can be compared to the rush of water out of a hose nozzle because of the small-appearing, but unfortunately too large, openings in the surface of the plunger tip made by the scoring by the hard aluminum oxide.

This is a continuation-in-part of my co-pending applications each titled Die Casting Machine Plunger Tip, filed November 17, 1958 and December 5, 1957, and Serial Numbered 774,804, now US. Patent 3,046,621, granted July 31, 1962 and 700,850, now abandoned, respectively.

Other and further objects and advantages of the present invention will be apparent from the following detailed description, drawings and claim, the scope of the invention not being limited to the drawings themselves as the drawings are only for the purpose of illustrating a way in which the principles of this invention can be applied.

Other embodiments of the invention utilizing the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claim.

3,692,88'fi Patented June 11, 1963 In the drawings:

FIG. 1 is a vertical cross section taken through a shot cylinder showing the internal details of the plunger tip of this invention;

FIG. 2 is a fragmentary cross sectional view taken vertically through the plunger tip and adjacent shot chamber of this invention showing the method of assembly; and

FIG. 3 is an exploded view of the plunger tip showing the component parts in perspective.

Referring to the drawings and more particularly to FIG. 1 the plunger tip of this invention is generally indicated by the numeral 200 and has a cylindrical body 210 which latter has a recess or counterbore 212 providing a cavity in its forward end.

A sealing ring 220 has outer sidewall surfaces 230 which are parallel to an axis provided by a longitudinal center of the shot cylinder 70, whereby the outer sidewall surfaces 236* fit the inner wall 240 of the cylinder 70.

The sealing portion 226) is disposed forwardly and in abutment with at least one forward wall surface of the cylindrical body 210 and such wall surface is shown at 244 having a transverse portion 246 and a second transverse portion 248 so called because it extends transversely to the axis of the shot cylinder 79 and sealing means 220.

Between the transversely extending portions 246 and 248 of the surface 244 is a forward and rearwardly extending portion 250 which latter has an inwardly extend ing protrusion 254 which is adapted to interlock with a complementally shaped recess 260 in the sealing member 220 whereby the sealing member 220 is securely held from movement forwardly or rearwardly with respect to the main body portion 21%.

The sealing member or ring 220 itself has its rearward side in abutment with the surface portions 246, 248, 250 and the protrusions 254 whereby the sealing member 220 is supported from moving rearwardly with respect to the main body portion 210.

As thus described the sealing portion 220 is prevented from being driven rearwardly with respect to the main body portion 21).

The sealing member 226 is of annular shape and has an opening 27% therethrough the surfaces of the wall of which are parallel to the axis of the shot cylinder 70 and are also substantially cylindrical along a major part of the surface 27 0.

The forward end of the inner surface 270 adjoins an outwardly curving convex forward inner corner 274 of the sealing means or ring 220 which latter receives in abutment against itself a concave and complementally curved surface 289 on the rearward side of a plunger tip plug or cap 284 and the cap 284 has a rearward portion 286 extending through the opening in the center of the annular sealing member or ring 220 which latter is defined by the surface 279.

The rearward portion 286 has an exteriorly outwardly facing surface 2% the major portion of which is elongated and in parallelism with the axis of a shot cylinder 70 of the sealing means or ring 220.

The exterior surface 294} tightly fits the inside of the sealing portion or ring 220 and also tightly fits the side wall of the recess 212 in the main body portion 210 and it will be seen that the walls at the sides of the recess 212 in the main body portion 210 also extend in parallelism with the axis of the shot cylinder 70 which is also the axis of the sealing portion or ring 220.

As thus described the construction of the plunger tip is such that the material of the sealing means or ring 229 can be formed of aluminum preferably or of a material of approximately the ductility and softness of aluminum whereby a force against the forward end of the plug or cap 284 will cause the cap 284 to move rearwardly forcing the sealing portion 224 outwardly whereby in produc- 3 tion the force of the shot metal against the plug 284 forces the sealing means outwardly to maintain a very close slidable fit between the sealing means or portion 220 and the inner wall of the shot cylinder 79 as prevents leakage.

The plunger tip main body portion 210 is provided with a threaded opening 300 extending therethrough for receiving the threaded forward end or stud 310 of a tubular plunger rod 312 which latter is hollow as best seen at 314 for permitting delivery of cooling fluids therethrough to enter into a hollow or concave rearward side 330 of the plug 284.

As best seen in FiG. 2, the method of making the plunger tip of PEG. 1 comprises placing a sealing member or ring 22% which has not yet taken final shape between the plug or cap 284 and the main body portion 210, the embryonic form of the sealing portion or ring 226 in the stage shown in FIG. 3 being defined by its being annular having an outwardly offset annular portion 350 on its outer side at its forward end and an inwardly olfset annular portion 352 extending inwardly on its inner side at its rearward end.

The rearward portion of the plug or cap 284 preferably has an outwardly facing corner 353 of circular shape which is rounded and convex on its rearward side.

With the plug 284 and the main body portion 210 of the shapes earlier described and of hard steel or other suitable material, and the sealing portion 224 being of soft metal such asaluminum, it will be seen that when the parts are in the positions as shown in FIG. 3 they can be pounded into the position shown in FIG. 2 by hitting the forward end of the plug 234.

As thus described it will be seen that the plunger tip of this invention is adapted by the relatively soft and ductile nature of the sealing member220, to provide a more effective'seal than has heretofore been possible whereby operation of the machine tends to force the plug 284 against the sealing means 220 pressing the latter against the shot cylinder for swedging it into a burnished fit. 7

From the foregoing description, it is thought to be obvious that a die casting machine shot cylinder plunger tip constructed in accordance with my invention is particularly well adapted for use, by reason of the convenience and facility with which it may be assembled and operated, and it will also betobvious that my invention is susceptible of some change and modification without departing from the principles and spirit thereof, and for this reason I do not wish to be understood as limiting myself to the precise arrangement and formation of the several parts herein shown in carrying out my invention in practice, except as claimed.

I claim:

A plunger for a die casting machine having a shot cyl inder in the bore of which the plunger is fitted and reciprocates to displace molten die casting metal from said shot cylinder, comprising 7 (A) a cylindrical metal body arranged coaxially in said shot cylinder with its periphery slidingly fitting said bore and having a coaxial concavity extending inwardly from one end thereof, said concavity having (a) a small internal diameter cylindrical inner end (1;) a larger internal diameter outer end (c) and said cylindrical body also having a protrusion projecting radially inwardly from the outer end of saidrlarger internal diameter cylindrical outer end of said concavity (B) a ring of soft ductile sealing metal having (a) a bore equal in size to and forming a continuation of said smaller internal diameter inner end of said concavity,

(b) a large external diameter cylindrical end closely fitting said bore of said shot cylinder,

(0) a smaller external diameter end completely filling said large internal diameter outer end of said concavity, and

(d) completely embedding said protrusion whereby said protrusion retains said ring of soft ductile sealing metal against axial withdrawal from said concavity,

(C) and a plug having (a) a cylindrical sleeve fitting within said bore of said ring of soft ductile sealing metal and also slidingly fitting said small internal diameter cylindrical inner end of said concavity,

(b) and a head fixed to and closing the outer end of said sleeve and engaging the outer end face of said ring of soft ductile sealing metal,

(D) whereby pressure of said molten die casting metal axially against the exterior of said head can displace said plug axially inwardly into said concavity and expand said ringtof soft ductile sealing metal (a) both axially into engagement with said bore of said shot cylinder (b) and also axially into engagement with said larger internal diameter outer end of said concavity behind said protrusion.

References Cited in the tile of this patent UNITED STATES PATENTS 2,110,379 Lannert Mar. 8, 1938 2,217,239 Smith Oct. 8, 1940 (2,485,526 Bennett Oct. 18, 1949' 2,804,666 Saives Sept. 3, 1957 2,856,656 Ring Oct. 21, 1958 2,932,865 Bauer Apr. 19, 19-60 

